1. Field of the Invention
The present invention relates to a method of manufacturing a radome disposed on the detection side of a radar that is mounted on a vehicle and detects an obstacle in the vicinity of the vehicle.
2. Description of the Related Art
In recent years, there has been a millimeter wave radar that is mounted on a vehicle and measures a distance or relative speed between the vehicle and an obstacle by detecting the obstacle in the vicinity of the vehicle by using a radio wave. A radiator grill made of a synthetic resin is provided on the detection side of the radar. An identification mark such as an emblem is provided in the middle of the radiator grill. A bright metal surface such as chrome plating is generally formed on a general radiator grill, emblem, or the like in order to provide a high quality feeling or texture. However, it is known that chrome plating prevents the transmission of radio waves. For this reason, there has been proposed a radar where an opening for transmitting radio waves is formed at a central portion of the radiator grill and a radome, which has metallic brilliance and is formed so as to transmit radio waves, is provided at the opening (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2000-49522 and Japanese Unexamined Patent Application, First Publication No. 2000-159039).
Here, in the above-mentioned Patent Documents, there is disclosed a radome that includes recesses, a deposition layer or a sputtered layer, and a resin layer. The recesses are formed on the back surface of a transparent resin layer (a surface facing a radar). The deposition layer or a sputtered layer is made of indium and is formed at the recesses as a metal layer having metallic brilliance. The resin layer includes protrusions corresponding to the recesses and is formed on the back surface of the transparent resin layer so that the thickness of the radome is substantially constant. The radome has metallic brilliance that does not cause an uncomfortable feeling even though the radome is disposed together with the radiator grill, and radio wave transmittance that is enough for the radar to detect an obstacle.
However, there are the following problems in the related art.
A coating film (a so-called base coating and top coating) or a colored layer is formed on the transparent resin layer of the above-mentioned radome by a coating step, a printing step, or the like. The coating film is provided to protect a metal layer that is formed by deposition or sputtering. The colored layer has a function as a mask that forms only the recesses as a bright metal surface. Further, the resin layer, which makes the thickness of the radome substantially constant, is formed on the surface of the transparent resin layer, on which the metal layer or the colored layer is formed, by injection molding.
A plurality of steps, such as a coating step and an injection molding step, other than a deposition step or a sputtering step, is required to form the radome as described above. Since these manufacturing steps are troublesome, certain defective products are generated. For this reason, there has been a problem in that it is difficult to suppress the rate of generation of defective products due to the reduction of the yield of products in all manufacturing steps.
In particular, since the metal layer, the coating film, or the like is damaged by injection pressure and the heat of a melted resin in the injection molding step, many defects such as indentation or peeling of a metal layer and a coating film have been generated.
The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a method of manufacturing a radome that can reduce the labor hours or the cost required to manufacture the radome by reducing the number of manufacturing steps and suppressing the rate of generation of defective products.